Multi-channel pump

ABSTRACT

A multi-channel pump and more particularly a peristaltic pump having a single casing carrying drive means, the casing including a portion for receiving from 1 to 10 or more individual pump units which are arranged in side by side relation, each of the pump units being independently operable by the drive means on the casing; each of the pump units being removably mounted on the casing for independent use or removal; each of the pump units carrying flexible tubing for peristaltic action by the pump unit; the drive means on the casing comprising a pair of spaced drive units operating at respectively different speeds, the pump units being adapted to be selectively arranged in either of two positions on the casing so as to operatively engage one of the drive units for operation at one speed or to operatively engage the other of the drive units for operation at the other speed.

United States Patent 1191 Fried et al.

1451 June 11, 1974 MULTI-CHANNEL PUMP [75] inventors: George Fried,Stamford, Conn.;

Oscar Botero, Woodside, NY.

[73] Assignee: Greiner Scientific Corporation, New

York, NY.

[22] Filed: Nov. 21, 1972 [21] Appl. No.: 308,418

[52] US. Cl 417/429, 417/475, 417/477 [51 Int. Cl. F04b 23/04, F04b43/08 [58] Field of Search 417/429, 475, 477, 476

[56] References Cited UNITED STATES PATENTS 1,123,712 l/l9l5 Driver417/429 2,376,917 5/1945 Hiltz 417/429 X 2,935,028 5/1960 Ferrari et al1 417/477 X 3,124,270 3/1964 Cornell 417/429 X 3,298,238 l/l967 Lea417/429 X 3,384,080 5/1968 Muller 417/477 X 3,507,585 4/1970 Mercer417/475 3,723,030 3/1973 Gelfand 417/477 X Primary Examiner-William L.Freeh Assistant Examiner-Richard E. Gluck [5 7] ABSTRACT A multi-channelpump and more particularly a peristaltic pump having a single casingcarrying drive means, the casing including a portion for receiving from1 to 10 or more individual pump units which are arranged in side by siderelation, each of the pump units being independently operable by thedrive means on the casing; each of the pump units being removablymounted on the casing for independent use or removal; each of the pumpunits carrying flexible tubing for peristaltic action by the pump unit;the drive means on the casing comprising a pair of spaced drive unitsoperating at respectively different speeds, the pump units being adaptedto be selectively arranged in either of two positions on the casing soas to operatively engage one of the drive units for operation at onespeed or to operatively engage the other of the drive units foroperation at the other speed.

16 Claims, 7 Drawing Figures PATENTEBJUR 11 m4 3.8161333 31m 1 or 3 FIGJW .mmasiiiiliW .imm W PAIENTEBJH 11 mm 38 16L033 SHEEI 2 OF 3 mun.

PATENTEDJUN 1 1 m4 3816L033 sum an; a

102 43 FIG-7 162 MULTI-CHANNEL PUMP BACKGROUND OF THE INVENTIONConventional peristaltic pumps are primarily of the single channel type,for pumping a single flow of liquid. If multiple flows of liquid orgases are required, a plurality of pumps each carrying its own drivemotor, must be used. This entails substantial pump costs.

More recently, it has been proposed, to provide pumps having a pluralityof channels associated with a single drive motor. However, the number ofchannels is fixed in such pumps and if the requirement is for morechannels than the fixed channel capacity of such pumps, then two or morepumps will be needed, again increasing overall pump costs.

Recent applications of peristaltic pumps requires substantial numbers ofchannels for simultaneous pumping. Thus, in ecology tests large andvarying numbers of reagent flow may be required and appropriate pumpingmeans must be provided. This normally entails the use of two or morecomplete pump units, each having its own motor drive. Since the cost ofthe motor drive is a substantial part of the overall pump cost, theinvestment in pumps can be substantial.

Further, with known multi-channel pumps, the rate of flow is uniform foreach channel. To have channels of different flow rates, separate pumpsmust be used, each pump having a desired flow rate. Here again, thepumps are inflexible and the separate pumps required represent largecapital investment.

Accordingly, an object of this invention is to provide an improvedmulti-channel peristaltic pump which has a single motor drive but isarranged to accommodate any given number of individual pump units, eachof the units being arranged for operation from the single motor drive;the units being quickly and easily operatively associated ordisassociated with the single motor drive.

Another object of this invention is to provide a pump of the characterdescribed, wherein the motor drive is located at one end of a casinghaving an open top portion, individual pump units being adapted to beremovably arranged in any desired number in side by side relation in theopen top portion of the casing, the motor drive including driving gearmeans and each pump unit including driven gear means for meshing withthe driving gear means by merely locating the units in the open topportion of the casing.

A further object of the invention is to provide a pump of the characterdescribed, wherein the individual pump units may be releasably locked onthe casing for operation and readily unlocked to allow for removal ofthe selected pump units from the casing; or for positioning the pumpunits on the casing in an inoperative position thereof.

Still another object of the invention is to provide a pump of thecharacter described, wherein the motor drive includes a pair ofelongated drive gears arranged to rotate at respectively differentspeeds, each pump unit having driven gear means for meshing with one ofthe elongated gears in one position of the pump unit on the casing, ormeshing with the other of the elongated gear means in another positionof the pump unit on the casing, thereby providing variations on pumpflow rates as well as any desired number of pumping channels.

Still another object of this invention is to provide improved individualperistaltic pumping units for use in a multi-channel pump having acasing and a single motor drive mounted thereon, such units including aperistaltic roller plate mounted between a pair of closely spaced platemembers, together with a backing member removably disposed between theplate members and in opposed relation to the roller plate for receivingtubing therebetween; the roller plate having peripheral driven portionsadapted to project below the lower edges of the plate members for drivenengagement with the motor drive.

Yet another object of this invention is to provide individual pumpassemblies of the character described which include latching means forlocking engagement with the casing with which the units are associatedto retain the units in selected operative or inoperative relationship tothe casing.

Still a further object of this invention is to provide a multi-channelperistaltic pump having a single motor drive for operating a variednumber of individual pump units; the individual pump units beingremovably mounted on a casing portion of the pump, thereby providing ahigh degree of flexibility in pumping varied flows of reagents or thelike, as required; and further, such pump units having alternativepositions on the casing portion of the pump to provide alternativepumping rates to thereby provide further flexibility in the operation ofthe pump as a whole.

Yet a further object of this invention is to provide a multi-channelperistaltic pump of the character described, which is of simpleconstruction; which has but a single motor drive for a varied number ofindividual pumping units; the pumping units being of a construction anda mode of association with the motor drive as to make the mounting,removal, or interchange of the pumping units quick and easy; andresulting in a moderate cost measured in terms of the substantial andvaried capacities of pumping units.

Other objects of this invention will in part be obvious and in parthereinafter pointed out.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a multi-channelpump embodying the invention;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a transverse sectional view thereof showing the arrangement ofdriving gears;

FIG. 4 is a side elevational view of a single pumping unit, with partsbroken away and parts in section;

FIG. 5 is a transverse view taken along the line 5-5 of FIG. 2, withparts in section; showing an individual pump unit mounted on a casingand in an inoperative condition;

FIG. 6 is a partial elevational view, similar to that of FIG. 5, showingthe individual pump unit disposed in one position on the casing foroperation at one speed;

and.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The instant invention isdirected essentially to a multi-channel pump, Le. a pump made up of aplurality of individual units, with each unit adapted to pump adifferent fluid reagent or the like. Further, such pump comprises asingle operating motor having drive means by which one or more pumpunits are driven simultaneously; and each pump unit being quicklyengaged with or disengaged from the drive means.

Further, the drive means of the pump may comprise a pair of drivemembers rotating at respectively different speeds; the individual pumpunits being adapted to be disposed in one position on the casing foroperation from one of the pair of drive members, or an alternativeposition on the casing for operation from the other of the pair of drivemembers.

Thus, as shown in FIGS. 1, 2, a multi-channel peristaltic pump embodyingthe invention, is generally indicated at 10. The same comprises a base Bincluding at one end thereof an enclosed motor casing generallyindicated at C and an open top cradle portion A extending from one sideof motor casing C for mounting scribed. The casing C comprises a bottomwall 11, up-

standing side walls 12, a top wall 13 and end walls 14, 15. Suitablespeed control means, not shown, is located within casing C and incircuit with motor M. The control knob 16 on top wall 13 regulates thespeed control means. An on-and-off switch and a reversing switch, notshown, are also disposed within casing C and suitably -connected incircuit with motor M. The control knobs 17, 18 on top wall 13,respectively operate said on-and-off, and reversing switches.

The open top cradle portion 10A comprises a bottom wall 11A, side wallportions 20, 21. Side wall portions 20A, 21A of angular cross sectionextend above side wall portions 20, 21 and terminate in outwardlyextending flange portions 22, 23. The outer edge of flange portions 22,23 are formed with longitudinally extending bead portions 24, 25 for thepurpose hereinafter appearingThe cradle portion 10A further includes anend wall 26.

The open space in cradle 10A, between walls 15 and 26 is adapted toaccommodate one or more individual pump units, generally indicated at 27and of a flat configuration. Such units are later described in detail.Any given number of pump units 27 may be arranged in cradle 10A, in sideby side relation and operated by motor M.

To this end, the output shaft 28 of motor M has a gear 28A fixed theretofor meshing with a similar size drive gear 29. ln turn, gear 29 mesheswith a larger idler gear 30 on a stub shaft 30A, which in turn mesheswith a drive gear 31 of similar size. Driving means extend from drivegears 29, 31 in the form of a pair of elongated gear members 33, 34respectively having reduced end portions 29A, 31A fixed to gears 29, 31,said gear members 33, 34 having longitudinally extending gear teeth 33A,34A respectively. The elongated gear members 33, 34 extendlongitudinally in cradle portion 10A adjacent bottom wall 11A thereofwith their axes in a common horizontal plane.

The gear members 33, 34 are journalled at their opposite ends by way ofreduced end portions 29A, 31A in suitable bearings, not shown, on walls15, 26. The comparative size of gears 29, 31 is such that gear 29 willoperate at a relatively high speed, whereas gear 31 will operate at arelatively low speed; such differential speeds being also respectivelytransmitted to gear members 33, 34.

Each of the flat pump units 27 is adapted to receive a single tubing T,or a pair of tubings T, T for suitable operation in a peristaltic mannerand thus pump a given reagent or other liquid or gases to the outputside of such tubings.

Thus, a pump unit 27 comprises a pair of similar thin metal plates 40,41. Plate 40 comprises a central portion 42 of generally rectangularshape with oppositely disposed, laterally projecting wing portions 43defined by an outer vertical edge 44, top edge 45, bottom edge 46. Thecentral portion 42 is further defined by inset depending vertical edgeportions 47 which extend from the inner ends of bottom edge 46. Portion42 is further defined by bottom edge portions 48 extending toward eachother and joined by a centrally disposed arcuate edge portion 49.

The top edge 50 of plate portion 42 terminates at its opposite ends inhooked portions 51 extending toward each other and defined in part byvertical edge portions 52 which merge at their lower ends with edges 45.

The elements forming a peristaltic pump structure are disposed betweenplates 40, 41. Thus, a circular roller plate 55 is mounted betweenplates 40, 41; said plate 55 having a hub portion 56 for mounting ashaft 57 carried in a bushing 58 fixed in plate portions 42. The plate55 is stiffened by integral radial ribs 59 projecting from one sidethereof. A series of molded nylon or other plastic rollers 60 arerotatably mounted on studs 61 fixed at one end thereof to peripheralportions of plate 55 on one side thereof. The periphery of plate 55 isformed with gear teeth 62 for selectively engaging teeth 33A of gearmember 33 or teeth 34A of gear member 34, when units 27 are mounted incradle 10A; the lower portions of said teeth 62 projecting below edge 49of plates 41, 42.

A protective thin shield 63 of molded plastic encloses A the upperportions of teeth 62 on plate 55. Shield 63 comprises an upper, annularskirt portion 64 of greater radial dimension than that of a lowerannular skirt portion 64. Shield portion 64 has a rim portion 64A whichoverlies teeth 62, FIG. 4. The shield 63 lies against the inner surfaceof roller plate 55, with inner annular edge thereof disposed between theinner edges of rollers 60 and the opposed surface of roller plate 55.

Combined spacer means and guide means for tubings T, or T, T" is locatedbetween plates 40, 41. To this end a pair of similar, molded plasticspacer members 65, 66 are disposed between plates 40, 41. The spacermember includes a portion 67 formed with a concave edge 68 for receivingrim portion 64A of shield 63; a bottom edge 69 coincident with edge 48of plate 41, and a right angle edge 70 coincident with edges 45, 52 ofplate 41.

Projecting outwardly of the inner surface of spacer member 65 is a Tshaped portion 71 having a vertical portion 72 abutting plates 40, 41and a horizontal portion 73 extending to plate 40 and having an innerend overlying the portion 64 of shield 63. Threaded bores 74, 75 areadapted to receive assembly screws 76 for securing plates 40, 41 to saidspacer members 65, 66.

Means is provided for providing a backing member for coaction withrollers 60 on roller plate 55 to act on the pump tubings T, T and T. Tothis end there is provided a flat molded plastic member 77 of yoke shapewith opposite end portions 78 interconnected by a central raised backupportion 79, having a concave bottom edge 80. The backing portion 79 isformed with a longitudinal slot 81 for receiving therein a stem member82 having reversely threaded, spaced opposite end portions 83, 84. Thestem member 82 is retained between the walls defining slot 81 by acollar 85 overlying said stem member and a grommet 86 holding saidcollar 85 in place.

A pair of cylindrical locking units 87 having threaded openings 88extending transversely thereof, are threaded on threaded portions 83, 84respectively of stem member 82. A knob 89 fixed to one end of stemmember 82 allows for rotation of stem member 82 in either direction tomove locking members 87 toward or away from each other. The inwardmovement of locking units 87 is limited by vertical edge portions 89 ofcentral portion 79. Locating pins 90 are mounted on end portions 78,projecting from one surface thereof.

It is understood that with backup member 77 separated from plates 40,41; the tubings T, or T, T" are disposed with their central portionsoverlying the rollers 60 and their opposite end portions overlyinghorizontal portions 73 of spacer members 65, 66. The backup member 77may then be mounted between the upper portions of plates 40, 41 and theconcave edge 80 thereof is properly located with respect to the opposedrollers 60, by the locating pins 90 which abut vertical edges 52 ofplates 40, 41.

The locking members 87, being in intially retracted positions on stemmember 82, readily clear the hooked portions 51 of said plates 40, 41.By rotating stem member 82 through knob 89, in the proper direction,locking members 87 are outwardly displaced to abut the hooked portions51 of plates 40, 41 to securely position backup means 77 in properrelation to the rollers 60 on roller plate 55, with the tubings T, or T,T" therebetween.

Means is provided for retaining the tubings T, T or T" againstlongitudinal shift when the pump unit 27 is in operation. To this end,horizontal outer end portions 91 of backup member 77 are formed withvertically extending threaded openings 92 to receive threaded pins 93.Friction shoes 94 are connected to the lower ends of pins 93 forrelative movement, with vertical guide portions 95 on said shoesreceived in appropriate guide slots 96 formed in portions 78. Rotatableknobs 97 fixed to pins 93 immediately above shoes 94, allow for adjustedvertical movement of said shoes 94. Friction strips 98 on the bottom ofshoes 94 and friction strips 98A on horizontal portion 73 of spacermembers 65, 66, which are in opposed relation to friction strips 98,afford means for engaging the tubing portions therebetween to preventslippage thereof.

Selected pump units 27 may be mounted in the eradle A, in side by siderelation, whereby the teeth 62 of roller plates 55 will mesh with theteeth 33A of drive gear 33 or with teeth 34A of drive gear 34, as willbe explained in detail.

Means is provided for releasably locking said pump units 27 on cradle10A. To this end, molded plastic latch members 100 are pivotally mountedbetween wing portions 43 of plates 40, 41. Latch members 100 are ofrectangular tab shape with outwardly projecting ears 101 at the upperend thereof for reception in openings 102 in plate portions 43 of plates40, 41 with O rings 104 on ears 101 to allow said latches to be pivotedto desired angular positions. The major portion of said latch membersdepend below edge 46 of plate portions 43. The latch members 100 areformed on their inner surfaces with transversely extending, verticallyspaced recesses 105, 106.

For locking said pump units 27 in operative engagement with gear members33 or 34; the units 27 are positioned in cradle 10A so that latchmembers 100 are pivoted to allow upper recesses 105 to engage bead edges24, 25 of cradle flanges 22, 23 as shown in FIGS. 6, 7.

If one or more of the pump units 27 is to be disengaged from operativeconnection to gear members 33 or 34, yet left in cradle 10A; the units27 are so positioned relative to cradle 10A so that the lower latchrecesses 106 receive bead edges 24, 25, thereby locking said units 27 oncradle 10A, with gear teeth 62 in spaced relation to gear teeth 33A,34A, of gear members 33, 34; as shown in FIG. 5.

It will be apparent that latch members 100 may be easily and quicklypivoted to either lock or unlock any of pump units 27 in relation tocradle 10A, to thereby facilitate mounting, removing or interchangingany number of pump units 27, as dictated by the pumping pattern desired.

Inasmuch as gear members 33, 34 respectively operate at differentspeeds, the rotational axis of geared roller plate 55 is so located onplates 40, 41, as to dipose the same in offset relation to the center ofthe spacing between gear members 33, 34 when the pump unit 27 is locatedon cradle 10A. It follows that pump units 27 may take alternatepositions on cradle 10A. In one case, teeth 62 of roller plate 55 engagethe teeth 33A of gear member 33, as shown in FIG. 6; while upon turningthe unit 27 through an angle of the unit 27 will be so positioned as tobring its gear teeth 62 in meshing relation with the gear teeth 34A ofgear member 34, as shown in FIG. 7.

The tubing T may be of conventional diameters and wall thicknesses, asknown in the peristaltic pump art. Either a single tubing T may beassociated with pump units 27, or in the case of very small diametertubings, a pair of such tubings t and T" may be used in a single pumpunit 27; see FIG. 1 and FIG. 2.

Knobs 16, 17 and 18 are manipulated to control motor speed; to reversethe motor and to stop and start the operation of the apparatus.

It will be apparent that with the pumping apparatus of the instantinvention, a single motor drive may operate a varied number of pumpingunits to provide different pumping patterns, depending on the number ofunits used; the number of tubings involved; and the selected positionsof the pump units on the cradle. Thus, the cost of providing asubstantial range of pumping patterns is kept at a minimum with the useof a single motor drive.

What is claimed is:

1. A multi-channel pump apparatus comprising base means, motor meansmounted on said base means, plural pump units adapted to be selectivelymounted on said base means, an elongated rotatable drive means mountedon said base means, said rotatable drive means being coupled to saidmotor means and adapted to drive said pump units, means for removablymounting each of said pump units on said base means, each of said pumpunits including fluid carrying tubing means extending into said units,means within each pump unit for progressively compressing said tubingmeans during operation, rotatable driven means formed on the outerperiphery of each of said pump units and adapted to engage saidelongated rotatable drive means at selected positions along the lengththereof to be driven thereby, said progressive compressing means mountedon said rotatable driven means, means for disengageably mounting each ofsaid rotatable driven means of said pump units to said pump unit drivemeans for individual and simultaneous operation.

2. Pump apparatus as in claim 1 wherein each of said pump unitscomprises a flat pump assembly, said assemblies being adapted to beselectively arranged in side by relation on selected portions of saidbase means for disengageable connection of each said operating meanswith said rotatable drive means.

3. Pump apparatus as in claim 2, wherein said drive means comprises anelongated gear member and each said driven means comprises gear meansfor meshing with said elongated gear member at selected positions alongthe length thereof in accordance with the position of the pump unit andits associated gear means relative to said base means.

4. Pump apparatus as in claim 2, and further including interengageablemeans on each of said pump assemblies and said base means for releasablylocking said assemblies to said base means.

5. Pump apparatus as in claim 2, and further including latch means forselectively releasably locking said pump units to said base means in oneposition in which said drive means is in disengaged relation to saiddriven means, or in another position in which said drive means is inengaged relation to said driven means.

6. Pump apparatus as in claim 2 wherein said drive means comprises apair of elongated gear members, means for rotating each of said pair ofelongated gear members at respectively different speeds and said drivenmeans comprises gear means, means for selectively positioning said pumpassemblies on said base means, whereby in one of said positions, saidgear means engages one of said pair of gear members for operation at onespeed and in another of said positions said gear means engages the otherof said pair of gear members for operation at another speed.

7. Pump apparatus as in claim 6 wherein said elongated gear members aredisposed in laterally spaced relation to each other, the axis of saidgear means being in laterally offset relation to the center of thelateral spacing of said pair of elongated gear members, whereby each ofsaid pump assemblies may be selectively disposed in one position on saidbase means whereby said gear means theroof meshes with one of said pairof elongated gear members or in another position on said base meanswhereby said gear means thereof meshes with the other of said pair ofelongated gear members.

8. Pump apparatus as in claim 3, wherein said base means comprises apair of longitudinally extending side walls providing an open top, and'apair of end walls connecting said side walls, said motor means beingdisposed outwardly of one of said end walls, said elongated gear memberextending longitudinally between said base side walls, said side wallsincluding longitudi nally extending flange portions extending from theupper edges thereof, each of said pump units including laterallyrelated, shoulder portions for seating on said base flange portions tolocate the lower peripheral edge portion of said driven gear meansbetween said base walls for engagement with said elongated gear member.

9. A pump apparatus as in claim 1 wherein said each pump unit comprisesa pair of opposed, spaced plate members, spacer means between said platemembers, a roller plate carrying roller members extending from one sideof said roller plate and along the periphery thereof, said roller platebeing rotatably mounted between said spaced plate members.

10. A pump as in claim 9 wherein said driven means comprises peripheralgear means on said roller plate.

11. A pump unit as in claim 9, and further including movable latch meansmounted between said spaced plate members to releasably lock said pumpunit to said base support means.

12. A pump unit as in claim 9 and further including movable latch meansmounted on said pump units for selectively releasably locking said pumpunits to said base means in one position in which said drive means is indisengaged relation to said driven means, or in another position inwhich said drive means is in engaged relation to said driven means.

13. A pump unit as in claim 9, and further including a backing memberdisposed between said plate members, in opposed relation to said rollermembers, said roller plate including driven means thereon for engagingwith the drive means on said base means when said pump unit isassociated with said base means.

14. A pump unit as in claim 13 wherein flexible tubing is adapted to bedisposed between said backing member and the roller members on saidroller plate, and adjustable friction means mounted on said spacer meansfor frictionally holding said tubing against shift relative to saidbacking means.

15. A pump unit as in claim 10 wherein said roller plate is disposedadjacent said spacer means, and further including shield means for thegear means on said roller plate for protecting said tubing against wear.

16. A pump unit as in claim 13, and further including coacting means onsaid backing member and said plate members for removably mounting saidbacking member between said plate members.

1. A multi-channel pump apparatus comprising base means, motor meansmounted on said base means, plural pump units adapted to be selectivelymounted on said base means, an elongated rotatable drive means mountedon said base means, said rotatable drive means being coupled to saidmotor means and adapted to drive said pump units, means for removablymounting each of said pump units on said base means, each of said pumpunits including fluid carrying tubing means extending into said units,means within each pump unit for progressively compressing said tubingmeans during operation, rotatable driven means formed on the outerperiphery of each of said pump units and adapted to engage saidelongated rotatable drive means at selected positions along the lengththereof to be driven thereby, said progressive compressing means mountedon said rotatable driven means, means for disengageably mounting each ofsaid rotatable driven means of said pump units to said pump unit drivemeans for individual and simultaneous operation.
 2. Pump apparatus as inclaim 1 wherein each of said pump units comprises a flat pump assembly,said assemblies being adapted to be selectively arranged in side byrelation on selected portions of said base means for disengageableconnection of each said operating means with said rotatable drive means.3. Pump apparatus as in claim 2, wherein said drive means comprises anelongated gear member and each said driven means comprises gear meansfor meshing with said elongated gear member at selected positions alongthe length thereof in accordance with the position of the pump unit andits associated gear means relative to said base means.
 4. Pump apparatusas in claim 2, and further including interengageable means on each ofsaid pump assemblies and said base means for releasably locking saidassemblies to said base means.
 5. Pump apparatus as in claim 2, andfurther including latch means for selectively releasably locking saidpump units to said base means in one position in which said drive meansis in disengaged relation to said driven means, or in another positionin which said drive means is in engaged relation to said driven means.6. Pump apparatus as in claim 2 wherein said drive means comprises apair of elongated gear members, means for rotating each of said pair ofelongated gear members at respectively different speeds and said drivenmeans comprises gear means, means for selectively positioning said pumpassemblies on said base means, whereby in one of said positions, saidgear means engages one of said pair of gear members for operation at onespeed and in another of said positions said gear means engages the otherof said pair of gear members for operation at another speed.
 7. Pumpapparatus as in claim 6 wherein said elongated gear members are diSposedin laterally spaced relation to each other, the axis of said gear meansbeing in laterally offset relation to the center of the lateral spacingof said pair of elongated gear members, whereby each of said pumpassemblies may be selectively disposed in one position on said basemeans whereby said gear means theroof meshes with one of said pair ofelongated gear members or in another position on said base means wherebysaid gear means thereof meshes with the other of said pair of elongatedgear members.
 8. Pump apparatus as in claim 3, wherein said base meanscomprises a pair of longitudinally extending side walls providing anopen top, and a pair of end walls connecting said side walls, said motormeans being disposed outwardly of one of said end walls, said elongatedgear member extending longitudinally between said base side walls, saidside walls including longitudinally extending flange portions extendingfrom the upper edges thereof, each of said pump units includinglaterally related, shoulder portions for seating on said base flangeportions to locate the lower peripheral edge portion of said driven gearmeans between said base walls for engagement with said elongated gearmember.
 9. A pump apparatus as in claim 1 wherein said each pump unitcomprises a pair of opposed, spaced plate members, spacer means betweensaid plate members, a roller plate carrying roller members extendingfrom one side of said roller plate and along the periphery thereof, saidroller plate being rotatably mounted between said spaced plate members.10. A pump as in claim 9 wherein said driven means comprises peripheralgear means on said roller plate.
 11. A pump unit as in claim 9, andfurther including movable latch means mounted between said spaced platemembers to releasably lock said pump unit to said base support means.12. A pump unit as in claim 9 and further including movable latch meansmounted on said pump units for selectively releasably locking said pumpunits to said base means in one position in which said drive means is indisengaged relation to said driven means, or in another position inwhich said drive means is in engaged relation to said driven means. 13.A pump unit as in claim 9, and further including a backing memberdisposed between said plate members, in opposed relation to said rollermembers, said roller plate including driven means thereon for engagingwith the drive means on said base means when said pump unit isassociated with said base means.
 14. A pump unit as in claim 13 whereinflexible tubing is adapted to be disposed between said backing memberand the roller members on said roller plate, and adjustable frictionmeans mounted on said spacer means for frictionally holding said tubingagainst shift relative to said backing means.
 15. A pump unit as inclaim 10 wherein said roller plate is disposed adjacent said spacermeans, and further including shield means for the gear means on saidroller plate for protecting said tubing against wear.
 16. A pump unit asin claim 13, and further including coacting means on said backing memberand said plate members for removably mounting said backing memberbetween said plate members.